As piezoelectric ceramics, ABO3-type ceramics such as lead zirconate titanate (hereinafter, referred to as “PZT”) is generally used.
However, PZT contains lead as an A-site element, and hence its effect on the environment is considered as a problem. Therefore, a piezoelectric material using a perovskite-type oxide containing no lead has been proposed.
For example, as a piezoelectric substance made of a perovskite-type oxide containing no lead, “Chemistry of Materials” 2006, Vol. 18, No. 21, pp. 4987-4989 describes Bi(Zn0.5Ti0.5)O3 as a Bi-based material. However, it is difficult to synthesize materials of Bi(Zn0.5Ti0.5)O3 and to polarize Bi(Zn0.5Ti0.5)O3 due to a high Curie temperature, and hence the piezoelectric performance thereof has not been clarified.
Further, a piezoelectric material containing BiFeO3 as a main component has been proposed. For example, Japanese Patent Application Laid-Open No. 2007-287739 discloses a BiFeO3-based material containing La in an A-site. BiFeO3 is a satisfactory ferroelectric substance, and reportedly exhibits a high amount of remnant polarization at low temperatures. However, BiFeO3 has a problem in that the displacement amount cannot be kept large under an electric field application due to its low insulation properties, which can be also found in view of containing Fe.
Further, “Chemistry of Materials” 2007, Vol. 19, No. 26, pp. 6385-6390 discloses a BiAlO3 piezoelectric material obtained by a high-pressure synthesis method. However, the piezoelectric performance of BiAlO3 has also not reached a practically applicable range yet.